Clinical course of hypertrophic cardiomyopathy in a regional United States cohort

Abstract

Context: Hypertrophic cardiomyopathy (HCM) has been regarded as a disease that causes substantial disability, with annual mortality rates of up to 6%, based largely on reports from tertiary referral centers.

Objective: To assess the clinical course of HCM in a patient cohort more closely resembling the true disease state.

Design: Retrospective cohort study.

Setting: A regional cohort from Minnesota and adjoining regions, free of referral center bias, studied at Minneapolis Heart Institute.

Patients: Two hundred seventy-seven consecutively studied HCM patients, none referred for specialized HCM care, managed clinically in a standard fashion.

Main outcome measures: Mortality and clinical course of HCM.

Results: During a mean (SD) follow-up of 8.1 (6.6) years, 45 patients died and 29 of these deaths were directly related to HCM; however, 8 of the 29 HCM deaths were not premature (occurring >75 years of age). Annual HCM mortality rate was 1.3% (0.7% for sudden cardiac death). Patients identified in adulthood (n = 234) showed no statistically significant difference in mortality when compared with expected mortality, as calculated for the general US or Minnesota populations (P=.17). Patients identified as children (n=43) showed decreased survival compared with the general population (P<.001). At most recent clinical evaluation, 192 patients (69%) had no or mild symptoms and 69 (25%) experienced incapacitating symptoms or HCM-related death; 53 (19%) of the patients had achieved estimated life expectancy of 75 years or older. More advanced symptoms at diagnosis-occurrence of atrial fibrillation (often associated with stroke), the presence of basal outflow obstruction of at least 30 mm Hg, and marked left ventricular wall thickness of more than 25 mm-were clinically important independent predictors of HCM mortality.

Conclusions: In a regionally selected patient population most closely resembling the true disease state, HCM did not significantly increase the risk of premature death or adversely affect overall life expectancy. Prevailing misconceptions of HCM as a generally unfavorable condition may largely be related to the skewed patient referral patterns characteristic of tertiary care centers. Hypertrophic cardiomyopathy is nevertheless a highly complex disease capable of serious clinical consequences and premature death in some patients.